The Common Language Runtime (CLR) in Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, and 4.5 does not properly check signatures, which allows remote attackers to make undetected changes to signed XML documents via unspecified vectors that preserve signature validity, aka "XML Digital Signature Spoofing Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A16559
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2013/ms13-040